Improvement in fusible plugs for steam-generators



I. F. MAHU'NEY. fusible Plug for Steam-Generators.

Patented M a rch 30',187 5.

No.16l,422.

Inve flier I W MQBXBMM THE GRAPHIC COJHOTOrLITHJQfifl PARK PLQOLN.

JAMES F. MAHONEY, OF ERIE, PENNSYLVANIA.

IMPROVEMENT IN FUSIBLE PLUGS FOR STEAM-GENERATORS.

Specification forming part of Letters Patent No. 161,422, dated March30, 1875; application filed March 19, 1875.

To all whom it may concern Be it known that I, JAIVIES F. MAHONEY, ofErie, in the county of Erie and State of Pennsylvania, have inventedcertain new and useful Improvements in Fusible Plugs forSteam-Generators; and I do hereby declare that the following is a full,clear, and exact description thereof which will enable others skilled inthe art to which it pertains to make and use the same, reference beinghad to the accompanying drawings, and to the letters of reference markedthereon, which form a part of this specification- Figure 1 being alongitudinal sectional elevation of a portion of a steam-generator withmy improvement attached thereto, showing the valve open and in a safeposition, or in the position in which it stands when the fusible plug isin perfect condition. Fig. 2 is a transverse section of line a: m ofFig. 1, showing the shut-off valve resting upon its seat, the fusibleplug in position, the valve-stem and the hand-wheel for operating it,and the slide for indicating the safe and dangerous positions of thevalve; and Fig. 3 is an elevation of Fig. 2, partly in section, showingthe slide as in a dangerous position, the fusible plug, the valve-seatwith an annular recess for controlling theheight of the water at thetime when the fusible metal in the plug shall melt.

Corresponding letters denote corresponding parts in the several figures.

This invention relates to fusible plugs for steam-generators, and to avalve and other appliances to be used in connection therewith. The useof fusible plugs in connection with some portion of everysteam-generator for the purpose of preventing injury thereto, caused byallowing the water to fall to too low a level, has become a recognizednecessity; and this invention has for its object to provide such a Iplug and devices to be used in connection therewith, which shall removethe objections which have heretofore been urged against them, and at thesame time render them more eflicient and less liable to cause delays inthe use of the generator, to which they are Y attached, and to this endit consists, first, in combining with a fusible plug a valve which canbe operated from the outside of the generator, and whereby the aperturein said plug can be closed when the fusible metal has been melted out,and thus the delay incident to such accidents be avoided. 0nd, itconsists in combining with the valve a slide which shall move therewith,and thus indicate to the person in attendance and others interested theposition of the valve. Third, it consists in combining with the recessedvalve-seat a detachable plug having a fusible plug inserted therein.Fourth, it consists in the combination of the parts hereafter specified,to constitute the complete apparatus.

In constructing devices of this character, I employ a valve seat orring, of metal,

A, upon one end of which there is formed a screw-thread for the purposeof screwing it in the crown-sheet ofthe fire-box of a steam-generator,or in some other portion thereof, the surface of which is, upon oneside, exposed to the action of the heat arising from the burning fuel,while the opposite side is in contact with the water within saidgenerator. Through the center of this there is made an aperture, whichis provided with a screwthread for the reception of a plug 13, throughwhich there is made an opening which is to be filled with fusible metal,as shown at B. This metal is to be made of an alloy of lead and tin, orother easily-fusible metals, such as will cause it to melt at anydesired temperature, according tothe pressure and temperature of thesteam to be carried within the generator, and is to be inserted in theaperture formed in the plug B, in such a manner as to cause it to form asteam-tight joint therewith and to cause its lower end to be exposed tothe action of the heated products of combustion in the fire-box.

In order that when in use the fusible metal may be melted before thewater in the generator has been allowed to fall to a level with thecrown-sheet of the fire-box, or below the same, and thus endanger theintegrity thereof, as well as the lives of persons in its vicinity,there is formed in that portion of the valve seat or ring A which iswithin the fire-box or flue an annular recess, 0, which surrounds theplug B, and extends upward to such a distance as to cause its upperportions to be above the crown-sheet or flue, so that as the Sec- 1water falls below the upper portion of said recess the heat from thefurnace will act upon the plug B to such an extent as to cause thefusible metal to be melted while the water is yet above the crown-sheet,and thus prevent the injuries incident to allowing it to fall below orto a level therewith. The valve seat or ring A extends above the sheetor flue for some distance. and has formed upon it a seat for the valveD, which is hinged to the lower end of a stem, E, furnished with ascrewthread, which works through a threaded aperture in a saddle or nut,F, placed upon the outer surface of the generator, its outer end beingprovided with a hand wheel or crank, G, for turning it. Upon the uppersurface of the saddle or nut F there is placed a stuffingbox, F, forpacking the rod E. When the parts just enumerated are in the positionsshown in Fig. 1 they are supposed to be in working order, the valve 1)being raised to such an extent as to cause the water to come in contactwith the fusible metal. In this position the parts will remain so longas the water is kept above the upper end of the annular recess in thevalve seat or ring A; but should it from any cause fall below such pointthe heat communicated from said recess to the plug B will melt thefusible metal therdn', which will have the effect to extinguish, orpartially extinguish, the fire, and will at the same time notify theattendant that his generator is in a dangerous condition. Under thepresent system, upon the occurrence of such a condition of things, greatdelay is caused in consequence of the fact that a new plug cannot beinserted until the generator has been allowed to cool down to such anextent as to make it possible for some person to enter and insert 'a newplug. This delay is often of great inconvenience, and especially is thisthe case when it occurs at sea or upon railroads, where an hours delaymay be fraught with serious consequences.

With my improvements, in connection with fusible plugs, the aperturecaused by the melting of the fusible metal may be closed at once byscrewing down the valve D upon its seat, and thus any delay be avoided,as the generator may continue to be used under such circumstances untilan opportunity is afforded for replacing the plug.

In order that persons other than those in immediate charge of thegenerator may know at a glance the condition of the apertures, there isattached to the upper end of the plate fixed to the saddle or nut F, thelatter having upon it the words safe and danger, the former being insuch a position as to admit of its being read when the fusible plug isin order and the valve is raised from its seat, as shown in Fig. 1,while the latter word can only be seen when the valve is screwed downupon its seat, as shown in Fig. 3.

To prevent the valve and indicating-slide from being tampered with, andthus made to deceive any person, a lock, L, is provided, which locks thevalve in its open position, and which may be sealed in the usual or anydesired way, and thus preclude the possibility of closing the valvewithout notice being given to the interested parties.

This apparatus is applicable to all forms of generators, whether they besupplied with large flues extending through them or with fire-boxes, asin the marine or locomotive type.

Having thus described my invention, what I claim, and desire to secureby Letters Patcut, is

1. In combination with a valve seat or ring containing a fusible plugfor use in steam-generators, an adjustable valve, which may be forceddown upon its seat or raised therefrom from the outside of thegenerator, substantially as and for the purpose set forth.

2. In combination with a valve for closing the aperture in a fusibleplug for use in steamgenerators, caused by the melting out of thefusible portion of the metal, a slide made to move with said valve, anda stationary seat, the parts being arranged substantially as and for thepurpose set forth.

3. The combination of the recessed valve seat or ring A and the plug BB, a portion of which is made of fusible metal, substantially as and forthe purpose set forth.

4. The combination of the recessed valve I seat or ring A, the valve D,rod E, clamp H,

tionary plate upon which it moves, substantially as and for the purposeset forth.

In testimony that I claim the foregoing as my own invention I affix mysignature in presence of two witnesses.

JAMES F. MAHONEY.

Witnesses:

G. M. OONNELL, E. A. BULLEY.

